Polarized sunglasses have been available for many years in which polarized lenses have been used to filter out reflections and in general to sharpen the viewed images of the surrounding scene. The polarization not only provides glare protection but also in some cases attenuates the overall light level such that the polarized glasses function not only as polarization lenses but also as light attenuating lenses.
The problem with such sunglasses is that in the newer instruments, such as cockpit dashboard-mounted instrumentation, there is a polarization layer over the display which is meant to enhance the display and cut down the effect of reflected light so that the display may be readily visible. This is true for aircraft cockpit instrumentation as well as, for instance, for instrumentation that is viewed outdoors, such as marine instrumentation, namely knotmeters, anemometers, wind direction and navigation instrumentation.
Moreover, in some automotive installations, the instrumentation is likewise provided with a polarized layer so as to make the display readily viewable in all light conditions. However, when one decides to view this instrumentation while using polarized sunglasses, the instrumentation appears black due to the cross-polarization in which no light comes through the sunglasses from the instrumentation itself. The result is that, in order to view the polarized displays, one must remove one's sunglasses, which is inconvenient at best and sometimes dangerous when, for instance, one is using the polarized sunglasses to view a scene and must switch one's gaze from the scene to the instrumentation, as in cases of emergency.
The result is that one uses non-polarized sunglasses, as do pilots, and therefore one does not attain the benefit of polarized sunglasses, which are substantially better at more sharply defining the viewed scene than are the non-polarized sunglasses. While these sunglasses do attenuate glare in various regions of the electromagnetic spectrum, they do not use the polarization component to effect such attenuations.